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Updated: Sep 28, 2025
Vitrification of In Vitro Matured Oocytes Collected from Adult and Prepubertal Ovaries in Sheep
Published on: July 10, 2021
Post thaw quality and viability of vitrified immature sheep oocytes using different cryoprotectant concentrations
K A Sofi1, B Qureshi2, A Shah3
1Div. Veterinary Clinical Complex, F.V.Sc and A.H, Shuhama, SKUAST-Kashmir, Srinagar, India. drsofi.vet54321@gmail.com.
Background:
The cryopreservation of oocytes through vitrification is quite successful but oocyte vitrification is still being standardized because of their structural and molecular sensitivity to the cooling and freezing processes.
Objective:
To evaluate the effect of different cryoprotectant concentrations on post-thaw morphology and viability of immature oocytes in sheep.
Materials And Methods:
Vitrification was achieved in three vitrification solutions comprised of different concentrations of the cryoprotectants ethylene glycol + DMSO, viz., (G1) 20%, (G2) 30%, (G3) 40% ethylene glycol + DMSO in equal ratio. Cryopreservation was in open pulled straws. Post vitrification evaluation was done after 1 week's storage in liquid nitrogen based on morphological evaluation and viability using trypan blue dye.
Results:
The present study revealed non-significantly higher morphologically normal oocytes in G3 (74.7%) followed by G2 (70.3%), and the lowest in G1 (66.6%). Morphological defects were observed in 33.3 %, 29.6% and 25.2% of oocytes after cryopreservation in 20% (G1), 30% (G2) and 40% (G3) vitrification solutions, respectively. The results were non-significantly different between vitrification solution groups. However, the viability of post thaw immature oocytes was 95.6%%, 84.4% and 81.1% after vitrification in G1 (20%), G2 (30%) and G3 (40%), with viability being significantly highest (P<0.05) in G1 (20%) and lowest in G3 (40%).
Conclusion:
Cryoprotectant concentrations enable the maintenance of normal morphology and minimize cryoinjury during vitrification of immature oocytes.
